The elucidation of the molecular control mechanisms that regulate tubule morphogenesis during kidney development provides a basis for developing novel therapeutic strategies for the treatment of the group of polycysfic kidney diseases resulting from genetic mutations including ADPKD. A body of evidence suggests that PKD-1 loss of function mutations result in dysfunctional regulation of tubulogenesis in development leading to dilatation of the tubule and formation of cysts. The PKD-1 gene product, polycystin-1 associates with components of the focal adhesion and cell-cell adherens complexes which function via JNK/AP-1 and Wnt/TCF/LEF signal transducfion pathways with impact on regulation of cell proliferation, repression of fetal gene transcription, cell adhesion and migration. Polycystin-1 is highly expressed in the basolateral membranes of the ureteric bud epithelium of normal developing kidneys consistent with an important role in development and regulation of differentiation of the kidney. We have developed and tested both retroviral and adeno-associated-virus (AAV) vectors for delivery and sustained gene expression in renal cell and organ cultures and plan to develop a series of expression vectors with polycystin-1 mutations for use in primary human renal epithelial cell culture experiments, metanephric kidney organ cultures and transgenic mice to test to develop a rational strategy for design of genetic therapeutic intervention. The aims of this project are: 1. to characterize the biological effects of a series of polycystin-1 mutants on tubulogenesis and the ADPKD cystic phenotype using AAV and retroviral gene delivery into tissue culture cells by transfection and into E11 mouse organ cultures by microinjection into the ureteric bud. 2. to characterize of the biological effects of the selected, most effective polycystin-1 truncation and overexpression mutants in transgenic mice 3. to determine whether re-activation of expression of the wild-type PKD-1 gene at various developmental stages during embryogenesis and postnatal life can ameliorate the course of cystic kidney disease using a Cre recombinase null mutant mouse. Important information will gained about mechanism of disease and effectiveness of gene therapy.